Controlling an insecticide-resistant bollworm in West Africa

Cotton is one of the most important cash crops in West Africa, contributing for more than half the income of some two million small-scale farmers cultivating on average about one hectare land. Cotton is being attacked by many pests, the cotton bollworm Helicoverpa armigera in particular, that developed high population densities in 1998 leading to yield reductions despite increased insecticide use in West Africa. A cotton network involving research, extension, cotton producing and chemical companies was created to prevent and manage resistance to insecticides. An insecticide resistance management (IRM) strategy was rapidly adopted by most West African farmers with the assistance of the extension services provided by the national cotton companies. The adoption of IRM over the next four years had a positive impact on the control of H. armigera populations leading to overall yield increases, however, with a 25% increase in protection costs.